The invention relates to a method for improving the
astaxanthin content of a dried
freshwater shrimp product through ultrasonic
blanching pretreatment, and belongs to the field of
deep processing of agricultural products. The method comprises the steps: selecting mature and fresh freshwater shrimps as raw materials; cleaning, removing
shrimp beards and empennages, and then carrying out variable-frequency ultrasonic
blanching pretreatment; in the first stage, putting pretreated freshwater shrimps into clear water according to a material-water ratio of 1 4, and setting the
water temperature to be 75-85 DEG C, the ultrasonic frequency to be 60KHz, the
power density to be 0.45-0.58 W / cm2 and the
treatment time to be 3-5min; in the second stage, taking out he freshwater shrimps and putting intoa NaCl solution with the
mass fraction being 2%-4%, wherein the material-
liquid ratio is 1 4, the
water temperature is set to be 65-75 DEG C, the ultrasonic frequency is set to be 25 KHz, the
power density is set to be 0.65-0.72 W / cm2 , and the
treatment time is set to be 4-6 min; and finally, performing normal-pressure hot
air drying, wherein the hot
air drying temperature is set to be 55-65 DEGC, the air speed is set to be 2.0-3.0 ms, and the
drying time is set to be 6-8 h. The variable-frequency ultrasonic
blanching effectively removes the fishy smell of the freshwater shrimps and reducesthe content of volatile basic
nitrogen in the dried products, and compared with conventional blanching, the fresh
amino acid content of the dried
freshwater shrimp products is increased by 17%-22%, and the
astaxanthin content is increased by 18%-23%.